title: Use of DNA microarray and small animal positron emission tomography in preclinical drug evaluation of RAF265, a novel B-Raf/VEGFR-2 inhibitor.
abstract: Positron emission tomography (PET) imaging has become a useful tool for assessing early biologic response to cancer therapy and may be particularly useful in the development of new cancer therapeutics. RAF265, a novel B-Raf/vascular endothelial growth factor receptor-2 inhibitor, was evaluated in the preclinical setting for its ability to inhibit the uptake of PET tracers in the A375M(B-Raf(V600E)) human melanoma cell line. RAF265 inhibited 2-deoxy-2-[(18)F]fluoro-d-glucose (FDG) accumulation in cell culture at 28 hours in a dose-dependent manner. RAF265 also inhibited FDG accumulation in tumor xenografts after 1 day of drug treatment. This decrease persisted for the remaining 2 weeks of treatment. DNA microarray analysis of treated tumor xenografts revealed significantly decreased expression of genes regulating glucose and thymidine metabolism and revealed changes in apoptotic genes, suggesting that the imaging tracers FDG, 3-deoxy-3-[(18)F]fluorothymidine, and annexin V could serve as potential imaging biomarkers for RAF265 therapy monitoring. We concluded that RAF265 is highly efficacious in this xenograft model of human melanoma and decreases glucose metabolism as measured by DNA microarray analysis, cell culture assays, and small animal FDG PET scans as early as 1 day after treatment. Our results support the use of FDG PET in clinical trials with RAF265 to assess early tumor response. DNA microarray analysis and small animal PET studies may be used as complementary technologies in drug development. DNA microarray analysis allows for analysis of drug effects on multiple pathways linked to cancer and can suggest corresponding imaging tracers for further analysis as biomarkers of tumor response.
authors.affiliation: Molecular Imaging Program at Stanford, Bio-X Program, Department of Radiology, Stanford University, Stanford, CA, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Tseng
authors.forename: Darrin
authors.initials: D
authors.lastname: Stuart
authors.forename: Kimberly
authors.initials: K
authors.lastname: Aardalen
authors.forename: Angelo
authors.initials: A
authors.lastname: Kaplan
authors.forename: Natasha
authors.initials: N
authors.lastname: Aziz
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Hughes
authors.forename: Sanjiv S
authors.initials: SS
authors.lastname: Gambhir
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005260:Female; D019788:Fluorodeoxyglucose F18; D020869:Gene Expression Profiling; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000627:therapeutic use*; D007124:Immunoenzyme Techniques; D015470:Leukemia, Myeloid, Acute / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000473:pathology; D008545:Melanoma / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D020411:Oligonucleotide Array Sequence Analysis; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000627:therapeutic use*; D012333:RNA, Messenger / Q000235:genetics; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013936:Thymidine / Q000378:metabolism; D014407:Tumor Cells, Cultured; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors*; D023041:Xenograft Model Antitumor Assays
chemical_list: D014408:Biomarkers, Tumor; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D012333:RNA, Messenger; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C559019:RAF265; D040301:Vascular Endothelial Growth Factor Receptor-2; C482120:Braf protein, mouse; D048493:Proto-Oncogene Proteins B-raf; D005947:Glucose; D013936:Thymidine